When a failure occurs in a routing processor that processes a packet on the Internet, the failure influences traffic of the Internet.
In order to minimize the influence, a dualization scheme is proposed, which includes a plurality of same routing processors to operate one routing processor in a master mode and residual routing processors in a slave mode. In this case, the routing processor that operates in the slave mode periodically communicates with the routing processor that operates in the master mode to synchronize routing data and state information of the routing processor, and as a result, when the failure occurs in the routing processor that operates in the master mode afterwards, the routing processor that operates in the slave mode can be operated in the master mode based on received routing data and state information. Accordingly, an external system cannot sense the failure of the routing processor that operates in a master mode and recognizes that the routing processor continuously operates.
In the case of a general dualization system, only one slave module is provided, and as a result, the operation mode is simply transited as described above.
When only one slave module is provided as described above, and even the slave module has the failure, there is also a problem that the entire system is down, and as a result, most of dualization systems include a plurality of slave modules in recent years.
As the related art, there is a technology in which residual slave modules operate in a new master mode according to a predetermined order when power of the master module is exhausted or the master module deviates from a private handy network, but an order of adding the slave module needs to be determined again, and an optimal slave module cannot be selected as the master module under a current system environment.
For example, when it is assumed that the priority is the order of slave module #1, slave module #2, and slave module #3 is assumed, in the case where the failure occurs in the master module, a subsequent master needs to be unconditionally slave module #1. In this case, a network environment of slave module #2 may be better than a network environment of slave module #1.